1. Field of the Invention
The present invention relates to wireless base stations and mobile stations used in a wireless communication system in which location registration is performed. Preferably, it relates to wireless base station and mobile stations used in a wireless communication system wherein the location registration areas are hierarchical (multilayered).
2. Description of the Related Art
System Configuration
FIG. 1 shows the configuration of a mobile (wireless) communication system. While there are communications systems based on various schemes, the description here takes as an example a W-CDMA (UTRA FDD) mobile communication system.
In the drawing, 1 is a core network, 2 is a wireless base station controller (RNC: Radio Network Controller), 3 is a wireless bases station (NodeB) and 4 is a mobile station (UE: User Equipment).
Core network 1 is a network used for routing in the wireless communication system. The core network can comprise for instance an ATM switched network, packet switched network, router network, etc.
Here, an example will be considered with two types of nodes that perform routing: MSC for nodes that perform routing of voice communication, etc (line switching), and SGSN for nodes that perform routing of packet communication, etc (packet switching).
Core network 1 is also connected to other public networks (PSTN), etc, enabling the mobile station 4 to communicate with stationary telephones and the like as well.
The wireless base station controller 2 is positioned as a higher level device of the wireless base stations 3, and is provided with a function of controlling these wireless base stations 3 (management of wireless resources used, etc).
Furthermore, the wireless base station controller 2 has the function of executing outer loop transmission power control and a handover control function, whereby the signal from a single mobile station 4 is received via a plurality of subordinate wireless base stations 3, and the data with the best quality is selected and transmitted to the core network 1 during handover.
The wireless base stations 3 carry on radio communication with the mobile station 4, with the wireless resources being managed by RNC 2. Furthermore, the wireless base stations 3 are provided with the function of executing inner loop transmission power control.
When the mobile station 4 is within the wireless area of a wireless base station 3, it establishes a wireless link to the wireless base station 3 and performs communication with other communication devices via the core network 1.
The interface between the core network 1 and RNC 2 is referred to as the Iu interface, the interface between RNCs 2 is referred to as the lur interface, the interface between RNC 2 and each wireless base station 3 is called the lub interface, and the interface between the wireless base station 3 and the mobile station 4 is called the Uu interface. The network formed by devices 2˜3 is referred to in particular as the radio access network (RAN).
Location Registration
Next, the location registration processing performed by the mobile station will be described using FIG. 2. FIG. 2 is a diagram illustrating the configuration of a location registration area.
In the drawing, 11, 12 and 13 are nodes which make up the core network 1, 11 represents an MSC (Mobile Switching Center), 12 represents an SGSN (Serving GPRS Support Node), and 13 represents an HLR (Home Location Register).
An MSC is a node which performs line switching for voice communication and the like, When performing reception of voice communication and the like to the mobile station 4, the MSC treats the wireless zone formed by the subordinate wireless base stations 3 as a single location registration area (LA #1, etc). The MSC has the function of calling the mobile station 4, and depending on the response from the mobile station 4, it establishes a communication path to mobile station 4 via one of the wireless base stations 3 making up the wireless zone in the location registration area in which the response was received.
SGSN is a node that performs packet switching. When performing reception processing of packet communication and the like to the mobile station 4, the SGSN treats the wireless zone formed by the subordinate wireless base stations 3 as a single location registration area (RA #1, etc). The SGSN has the function of calling the mobile station 4, and depending on the response from the mobile station 4, it establishes a communication path to mobile station 4 via one of the wireless base stations 3 making up the wireless zone in the location registration area in which the response was received.
HLR 13 is a data base for managing the current location of the mobile station 4, which makes it possible to specify the area for calling the mobile station 4 for voice and packet communication.
Namely, the mobile station 4 moves between zones formed by the wireless base stations 3, and detects the location registration area it is in based on area information announced by the wireless base stations 3. When there is a change in the location registration area stored by the mobile station in question, location registration is performed via a wireless base station 3 to update the current location managed by the HLR. The current location of the mobile station 4 is thereby updated as the mobile station 4 moves, making it possible for the HLR 13 to manage and store the most recent current location of the mobile station 4.
While FIG. 2 shows distinct LAs and RAs, it is also possible to unify the two areas and manage the location of the mobile station 4 based on the LA only, with the MSC 11 and SGSN 12 calling the mobile station 4 for voice communication and packet communication using LA as a unit.
Literature relating to location registration includes the following publicly known literature: Japanese Unexamined Patent Application Publication S61-18229
Since the location of mobile stations in a mobile communication system needs to be managed, the mobile station stores the previously registered location registration area, and if the stored location registration area is different from the location registration area detected based upon announcement information from a wireless base station, updating of the location registration area is determined to be necessary, and location registration area updating (location registration) with HLR is performed via the wireless base station.
However, since location registration requires exchanging wireless signals with a wireless base station, wireless resources are consumed during location registration.
In particular, when a plurality of mobile stations moves simultaneously by means of a mass transit means (train, bus, airplane, bus, etc), they will perform location registration simultaneously with the same wireless base station. This leads to problems such as a large amount of wireless resources being consumed at once due to the concentration of location registrations, and a temporary increase in the processing load of the nodes performing processing involved in location registration (MSC, SGSN, HLR, etc).